Temperature Sensor Errors: Short Circuit to Ground

Hello,

A friend of mine is experiencing the following problem with his Audi 80 B4 TDI (1Z), manufactured in 1994:
The car has lost power and can only accelerate up to about 100 km/h. I've already done some troubleshooting and tested the needle lift valve (see a few threads below). The effect was that the car wouldn't start at all .
Now, a friend has cleared the error memory, and the engine at least starts again . However, there are still many error entries present:
Fuel temperature, intake manifold temperature, and coolant temperature to some freezing temperature, and short circuit to ground. Similarly, mass airflow sensor -> short circuit to ground .

I wasn't present during the memory reading and clearing process, so I can't provide more details, but has anyone else experienced all of these errors at the same time? It sounds a bit like a broken cable in a common ground line... Unfortunately, the mechanic is also at a loss.

It could also be a faulty engine control unit (ECU). Is there a way to have this tested somewhere (e.g., at a Bosch service center?), or possibly repaired? I'm not really keen on the workshop replacing the ECU based on suspicion, as it's likely to be very expensive.

Thank you & best regards,
Stefan

Deleted upon request.

Hello,

First of all, thank you to 'diesel.gustav'!
I'll soon be equipping myself with a multimeter to start searching and measuring the wires. Two mechanics have already tried this (with a wiring diagram), and as far as I understand, they measured 5 volts on various sensors. So, the voltage supply from the control unit seems to be working. It seems that the common ground wire to pin 33 is the only remaining possible source of error .
I hope it's not a defect in the control unit itself. If there isn't a clearly visible cold solder joint, I'm pessimistic about what can be repaired .

If I come up with a solution, I will definitely post it.

Thank you & best regards,
Stefan

Hi,

My 1Z also had that problem before.
A short circuit in a cable within the wiring harness caused a ground conductor rail in the STG (System Test Generator) to burn out – a pretty cool failure.